Surface waveguide transition section



JUL 1959 w. c. WILKINSON, JR 2,867,776

SURFACE mwscums mnsmou SECTION Original Filed April 12, 1950 ,42 \POL YSTYffA/E INVENTOR William 62 Wilkinson 7 1m ATTORNEY United States Patent SURFACE WAVEGUIDE TRANSITION SECTION William C. Wilkinson, Jr., West Windsor Township, Mercer County, N. 1., assiguor to Radio Corporation of America, a corporation of Delaware Continuation of application Serial No. 155,480, April 12, 1950. This application December 31, 1954, Serial No. 479,153

14 Claims. (Cl. 333-21) This invention relates to waveguides, and more particularly to transition sections between hollow pipe and surface transmission waveguides.

This application is a continuation of application Serial No. 155,480, filed April 12, 1950, now abandoned.

Hollow pipe and surface waveguides for the transmission of electromagnetic energy are coming into greater use with the increase of efficiency of the generators of high frequency. Surface waveguides and hollow pipe waveguides each guide energy from one place to another. The hollow pipe waveguides enclose the electromagnetic fields. The energy is in the fields outside a surface waveguide, although partially within the guiding rod if it is of dielectric material, and entirely outside the rod only in some cases of metallic rods. It is often a problem to transfer energy efiiciently from one type of waveguide to the other type.

It is an object of the present invention to transfer energy efficiently between a hollow pipe waveguide and a surface waveguide.

Another object of the invention is to improve the transfer of energy between such waveguides.

A further object of the invention is to increase the percentage of energy transfer between a hollow pipe and surface waveguide.

These and other objects, advantages, and novel features of the invention will be more apparent from the following description when taken in connection with the accompanying drawing in which like reference numerals refer to like parts and in which:

Fig. 1 is a diagram schematically illustrating an electromagnetic energy transmission system using hollow pipe and dielectric surface waveguides including a longitudinal cross-sectional view of a transition section between the waveguides;

Fig. 2 is a longitudinal cross-sectional view of an alternative transition section which may be used in place of the one in Fig. l and which employs a horn termination on the hollow pipe waveguide; and

Fig. 3 is a longitudinal cross-sectional view of a highly efiicient transition section according to the invention utilizing a dielectric lens.

In accordance with the invention, the transition section between hollow pipe and surface waveguides includes a smoothly joined extension of one of said waveguides increasing in transverse cross-sectional perimeter with distance toward the other waveguide. Thus, in the transition section, one may use a horn terminating the hollow pipe waveguide and facing the dielectric waveguide or one may use a flared section of the surface waveguide enlarging toward the hollow pipe waveguide. In a preferred form of the invention, a dielectric lens between the two waveguides is found to improve the energy transference.

Referring now more particularly to Fig. l, a source supplies high frequency energy to a hollow pipe waveguide 12 which in this instance is circular. The connection 14 between the source and waveguide 12 may be any of many well known conventional connections to "ice supply energy to the hollow pipe waveguide. The waveguide 12 is in this instance of circular cross section. Between the hollow pipe waveguide 12 and a dielectric rod 18 is a transition section 16. The dielectric rod waveguide 18 is in this instance circular in transverse cross section. Transition section 16 includes an extension 20 of the rod 18 which increases in transverse cross sectional perimeter and diameter with distance from the rod 18 toward the waveguide 12. The maximum diameter of the rod extension 20 is in the plane 22, that plane at which an extension 24 of waveguide 12 terminates. A further extension 26 continues from the extension 20 decreasing in transverse cross section perimeter with distance toward waveguide 12. The further extension 26 is tapered to a point on the axis of the extension 24. The rod waveguide 18 may carry energy from the transition section 16 to a load 27. The connection between the load 27 and the section 18 may be a transi tion section similar to that of 16 but transferring energy in the reverse direction, as will be understood by those skilled in the art.

Instead of the transition section 16 the section 48 of Fig. 2 may be employed. In this example. the waveguide 12 has an extension 30 smoothly joined thereto. The horn section 30 increases in transverse cross sectional perimeter with distance from waveguide 12 to waveguide 18. Surface waveguide 18 has an extension 32 which extends within and terminates within the horn 30.

A still further transition section 34 is illustrated in Fig. 3 which uses a horn 30 which may be the same as that of Fig. 2. A lens 36, preferably of dielectric material, has a diameter to just close the mouth of horn 30 at the termination of the mouth. Dielectric surface waveguide 18 in this instance terminates outside the horn mouth. The convergent dielectric lens 36 is between the waveguides 12 and 18. The transition sections 16, 43, and 34, when used, each has its longitudinal axis in alignment with the axis of waveguides 12, 18.

Of the three sections shown, that of Fig. 3 has been found to be the most eflicient. Waveguide 12 may comprise a circular copper tubing of 3/1 inch in internal diameter through which the energy is propagated from the source 10 in the TE mode, at an operating frequency corresponding to a wavelength in air of 1.25 centimeters. The surface waveguide may comprise a dielectric rod of polystyrene circular in cross-section and Vs inch in diameter. The lens 36 may be of polystyrene with a focal length of 3 inches and a maximum distance along the optical axis between diffracting surfaces of 0.650 inch. The horn mouth at its greatest internal diameter and the lens 36 preferably are about 3 inches in diameter. The dielectric rod surface waveguide 18 preferably terminates /2 inch from the surface of lens 36. The horn is 3% inches long axially. The assembly in accordance with Fig. 3 having the foregoing dimensions was found to be the most efficient of the various transition sections shown above and is therefore considered a preferred embodiment at the present time. However, it should be noted that even though that of Fig. 3 has been found the most efiicient embodiment, it may be desirable for reasons of simplicity or otherwise to employ one of the transition sections 16 or 48. The transition sections disclosed herein may readily be adapted to other types of surface waveguides, such as those disclosed in the application of Charles H. Chandler, Serial No. 155,475, filed April 12, 1950, and titled Surface Waveguide Systems."

From the foregoing, it is apparent that the transition section of the invention is simple and convenient in construction, provides a high efiiciency of energy transference, and is particularly useful in systems in which it is desired to transmit energy along surface waveguides.

What is claimed is:

1. A waveguide transmission system for electromagnetic energy comprising, in combination, a hollow pipe waveguide; an outwardly flaring horn extension axially aligned with said waveguide smoothly joined at the smaller end thereof to said waveguide and open at the larger end thereof; a surface wave rod waveguide spaced a predetermined distance from the open end of said horn extension and having a longitudinal axis aligned with the common axis of said horn extension and hollow pipe waveguide; and an electromagnetic energy focusing system including at least one dielectric lens formed with curved refractive surfaces and having a given focal length and an optical axis, said dielectric lens being mounted in said horn extension with the optical axis thereof aligned with said common axis, said focal length of said one dielectric lens being greater than the spacing between said dielectric lens and said surface wave rod waveguide.

2. A waveguide transmission system for electromagnetic energy comprising, in combination, a hollow pipe waveguide; an outwardly flaring horn extension axially aligned with said waveguide smoothly joined at the smaller end thereof to said waveguide and open at the larger end thereof; a dielectric rod waveguide spaced a predetermined distance from the open end of said horn extension and having a longitudinal axis aligned with the common axis of said horn extension and hollow pipe waveguide; and an electromagnetic energy focusing system including at least one dielectric lens formed with curved refractive surfaces and having a given focal length and an optical axis, said dielectric lens being mounted in said horn extension at said open end thereof with the optical axis thereof aligned with said common axis, said focal length of said one dielectric lens being greater than said distance between the open end of said horn extension and said dielectric rod waveguide.

3. A waveguide transmission system for electromagnetic energy comprising. in combination, a hollow pipe waveguide; an outwardly flaring horn extension axially aligned with said waveguide smoothly joined at the smaller end thereof to said waveguide and open at the larger end thereof; a dielectric rod waveguide spaced a predetermined distance from the open end of said horn extension and having a longitudinal axis aligned with the common axis of said horn extension and hollow pipe waveguide: and an electromagnetic energy focusing system consisting of a single lens formed solely of dielectric material and having bi-convex refractive surfaces, said lens having a given focal length and an optical axis,

said lens being mounted in said horn extension at said open end thereof with the optical axis thereof aligned with said common axis, said focal length of said lens being substantially larger than said distance between the open end of said horn extension and said dielectric rod waveguide.

4. A transition section for the transfer of electromagnetic energy between a hollow pipe waveguide and a dielectric rod waveguide spaced from said hollow pipe waveguide and axially aligned therewith comprising, in combination. an outwardly flaring metallic horn located between said two waveguides and axially aligned with the common axis thereof, said horn being smoothly joined at the smaller end thereof to said hollow pipe waveguide and open at the larger end thereof; and a single electromagnetic energy focusing lens formed solely of dielectric material mounted in said horn extension at said open end thereof, said lens having an optical axis aligned with said common axis and having a focal length which is substantially larger than the space between the open end of said horn and said dielectric rod waveguide.

5. A waveguide transmission system for electromagnetic energy comprising, in combination, a hollow pipe waveguide; an outwardly flaring horn extension axially aligned with said waveguide smoothly joined at the smaller end thereof to said waveguide and open at the larger end thereof; a surface wave rod waveguide spaced a predetermined distance from the open end of said horn extension and having a longitudinal axis aligned with the common axis of said horn extension and hollow pipe waveguide; and an electromagnetic energy focusing system having a given focal length and a focal axis, said focusing system being mounted in said horn extension with the focal axis thereof aligned with said common axis, said focal length of said focusing system being greater than the spacing between said focusing system and said surface wave rod waveguide.

6. An open waveguide system for a predetermined frequency range comprising a surface wave waveguide, hollow, circular launching means for launching a beam of wave energy in the TE mode onto said surface wave waveguide and for coupling said surface wave waveguide to said launching means to cause substantially continuous transition from the field of said beam to that of said surface wave waveguide and to propagate said wave energy substantially in the space outside of said surface wave waveguide and in the axial direction thereof, said energy being contained substantially within a predetermined cylindrical space coaxial and coextensive with said surface wave waveguide at a frequency within said frequency range and of a diameter substantially equal to that of said beam at a frequency within said frequency range.

7. A waveguide transmission system as set forth in claim 5, wherein the spacing between said focusing system and said hollow pipe waveguide is approximately one said focal length.

8. A waveguide transition section comprising a ho]- low conductive waveguide, a dielectric surface waveguide, said waveguides being positioned with one end of one waveguide near to but spaced from one end of the other waveguide, said ends being devoid of any metallic connection therebetween, one of said waveguides having a tapered section at said one end thereof that is made of material similar to the material of said one waveguide and that increases from the configuration of said one waveguide at said one end to a larger configuration in a direction toward said other waveguide, said tapered section transferring wave energy between said waveguides.

9. A waveguide transition section comprising a hollow, conductive, cylindrical waveguide, a cylindrical rodlike, dielectric surface wave waveguide, said waveguides being positioned with their longitudinal axes positioned along a common straight line and with one end of one waveguide near to but spaced from one end of the other waveguide, said ends being devoid of any metallic connection therebetween, one of said waveguides having a tapered section at said one end thereof that is made of the same material as said one waveguide and that increases from the circumference of said one waveguide at said one end to a larger circumference in a direction toward said other waveguide, said tapered section transferring wave energy between said waveguides.

10. An electromagnetic waveguide transition section comprising a hollow, cylindrical waveguide made of a conductive material, a cylindrical, rod-like, surface wave waveguide made of a dielectric material, said surface wave waveguide having a smaller diameter than said hollow waveguide, said waveguides being positioned so that their longitudinal axes lie along a common straight line and so that one end of one waveguide is spaced from one end of the other waveguide, said ends being devoid of any metallic connection therebetween, said surface wave waveguide having a tapered section of said dielectric material at said one end thereof that increases in cross-section from the circumference of said surface wave waveguide at said one end to the larger circumference of said hollow waveguide and that decreases from said larger circumference of said hollow waveguide to a point in a direction toward said hollow waveguide, said hollow waveguide having a uniform cross-section at said one end thereof, and means for positioning at least a portion of said tapered section between said point and said larger circumference within said hollow waveguide so that said tapered section transfers electromagnetic wave energy between said waveguides, said wave energy being conducted substantially within a predetermined space coaxial with and coextensive with said surface wave waveguide.

11. An electromagnetic waveguide transition section comprising a hollow, cylindrical waveguide made of a conductive material, a cylindrical, rod-like, surface wave waveguide made of a dielectric material, said waveguides being positioned so that their longitudinal axes lie along a common straight line and so that one end of one waveguide is adjacent one end of the other waveguide, said ends being devoid of any metallic connection therebetween, said hollow waveguide having a tapered section of said conductive material at said one end thereof that increases in cross-section from the circumference of said hollow waveguide at said one end to a larger circumference in a direction toward said surface wave waveguide, said surface wave waveguide having a uniform crosssection at said one end thereof, and means for positioning at least a portion of said surface wave waveguide within but spaced from said tapered section of said hollow waveguide so that said tapered section transfers electromagnetic wave energy between said waveguides, said wave energy being conducted substantially within a predetermined space coaxial with and coextensive with said surface wave waveguide.

12. An electromagnetic waveguide transition section comprising a hollow, cylindrical waveguide made of a conductive material, a cylindrical, rod-like, surface wave waveguide made of a dielectric material, said waveguides being positioned so that their longitudinal axes lie along a common straight line and so that one end of one waveguide is adjacent one end of the other waveguide, said ends being devoid of any metallic connection therebetween, said hollow waveguide having a tapered section of said conductive material at said one end thereof that varies uniformly in cross-section from the circumference of said hollow waveguide at said one end to a larger circumference in a direction toward said surface wave waveguide, and said surface wave waveguide having a uniform cross-section at said one end thereof, and a lens made of a dielectric material and having convex surfaces positioned in said tapered section so that the focal point of said lens lies on said straight line and so that said tapered section transfers electromagnetic wave energy between said waveguides, said wave energy being conducted substantially within a predetermined space coaxial with and coextensive with said surface wave waveguide.

13. A waveguide transmission system for electromagnetic wave energy, comprising, in combination, a hollow pipe waveguide, an outwardly flaring horn extension axially aligned with said waveguide and joined at the smaller end thereof to said waveguide and open at the larger end thereof, a dielectric rod-like surface wave waveguide having a longitudinal axis aligned with the common axis of said horn extension and said hollow pipe waveguide said surface waveguide being near to but spaced from said horn extension and said hollow pipe waveguide and being positioned in energy transfer relation with said horn extension, the space between the end of said surface wave waveguide and the nearest end of said hollow pipe waveguide and said horn extension being free, unobstructed, and devoid of any metallic connection.

14. A waveguide transmission system for electromagnetic wave energy, comprising, in combination, a hollow pipe waveguide, an outwardly flaring horn extension axially aligned with said waveguide and joined at the smaller end thereof to said waveguide and open at the larger end thereof, a dielectric rod-like surface wave waveguide entering into said horn from the open end thereof so that its longitudinal axis is aligned with the common axis of said horn extension and said hollow pipe waveguide said surface waveguide being near to but spaced from said horn extension and said hollow pipe waveguide and being positioned in energy transfer relation with said horn extension, the space between the end of said surface wave waveguide and the nearest end of said hollow pipe waveguide and said horn extension being free, unobstructed, and devoid of any metallic connection.

References Cited in the file of this patent UNITED STATES PATENTS 2,129,711 Southworth Sept. 13, 1938 2,438,795 Wheeler Mar. 30, 1947 2,556,046 Simpson June 5, 1951 2,588,610 Boothroyd Mar. 11, 1952 2,595,078 Iams Apr. 29, 1952 2,617,880 Iams Nov. 11, 1952 2,625,605 Chandler Jan. 13, 1953 2,659,817 Cutler Nov. 13, 1953 2,685,068 Goubau July 27, 1954 2,688,732 Kock Sept. 7, 1954 OTHER REFERENCES "A new type of wave transmission," The Wireless Engineer, vol. XIH, No. 153, June 1936, pages 291-3. 

